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Model Forum / General / Rockets / August 2003Tear-drop shaped rockets
I've seen egg and bowling ball lofters with this efficient shape do very well, and I know it is a subsonic design. Can someone give me the quick tradeoffs between this design and a minimum diameter model with respect to a maximum altitude flight in a model that does not actually REQUIRE a larger forward diameter? This will be an Estes "E" motor model rocket. Basically, I'm curious why we don't see the tear-drop in more general purpose rockets. My sims are showing an advantage to the tear-drop over a minimum diameter model. Playing with ideas for a new project. TIA  SignatureGary Bolles NAR 82636 summum jus, summa injuria est To contact me; bollesg at comcast dot net http://home.comcast.net/~bollesg/rockets/rockets.html > I've seen egg and bowling ball lofters with this efficient shape do very > well, and I know it is a subsonic design. [quoted text clipped - 9 lines] > > Playing with ideas for a new project. The tear drop shape is practical only when something is constraining your rocket size to something larger than the motor diameter. An egglofter is a perfect example. The screwy FAI rules are another, where all altitude and duration events require Big Bertha sized rockets. But I've only seen one person build teardrop FAI models to their minimum diameter requirements, over a decade ago. There is no advantage to taking a minimum diameter rocket and say doubling its diameter so that you can make it teardrop shaped. The frontal area goes up faster than the Cd comes down. BTW, I've backtracked teardrop egglofters to a Cd of less than 0.2. But with twice the diameter of a 24mm rocket the CdA comes out larger than a minimum diameter rocket with even a Cd of 0.7. Or an 18mm rocket with a CdA of 1.4! Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD! <<< Kaplow Klips & Baffle: http://nira-rocketry.org/LeadingEdge/Phantom4000.pdf www.encompasserve.org/~kaplow_r/ www.nira-rocketry.org www.nar.org Save Model Rocketry from the HSA! http://www.space-rockets.com/congress.html |
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